Intra-Annual Variation in River-Reservoir Interface Fish Assemblages: Implications for Fish Conservation and Management in Regulated Rivers

Abstract

While much is known about the fish assemblages, habitats, and ecology of rivers and reservoirs, there has been limited study of the fish assemblages in transitional habitats between these lotic and lentic habitats. Data about these river–reservoir interface (RRI) fish assemblages are needed to guide integrated management efforts of river–reservoir ecosystems. The aim of these efforts is to recommend flows for natural river function, conserve native riverine fish assemblages, and maintain reservoir sport fisheries. We used a multigear approach to assess the fish assemblages of four RRIs in the Colorado River Basin, Texas. In addition to characterizing RRI fish assemblages using species richness and evenness metrics, and habitat‐use guilds, we used a multivariate approach to evaluate intra‐annual shifts in species composition and abundance. All RRIs had high species richness and evenness values and included both macrohabitat generalist and fluvial species. RRIs also contained high proportions of the fish species available within each river–reservoir ecosystem, ranging from 55% to 80%. Observed intra‐annual shifts in RRI fish assemblages resulted from changes in abundance of dominant species rather than changes in species composition, with abundance of most species increasing from early spring to summer. Fish species responsible for intra‐annual shifts included mostly floodplain and migratory species, suggesting that species both used littoral habitats within RRIs and migrated through RRIs to river and reservoir habitats. The diversity of fishes found within RRIs highlights the importance of including these areas in future conservation and management efforts of river–reservoir ecosystems. Copyright © 2013 John Wiley & Sons, Ltd.

Razorback Sucker Movement Strategies across a River–Reservoir Habitat Complex

“…Our results also identified 40 fish that moved between the reservoir and the river in different seasons, showcasing potential intraspecific variation in movement strategies within Razorback Sucker. Reservoirs are common features in contemporary riverscapes, but data is lacking on the role they play in population and community dynamics, particularly for native species (Miranda et al 2010;Buckmeier et al 2014;Fischer and Quist 2019). Reservoir inflows provide close proximity and critical habitats for some fish, such as highly productive transitionary habitats next to adequate spawning habitat (Thornton et al 1990;Miranda et al 2017;Albrecht et al 2018).…”

Waterfall formation at a desert river–reservoir delta isolates endangered fishes

“…Despite the acknowledgment of fragmentation effects in conceptual models of riverine function (e.g., Stanford & Ward, ) and negative interactions of reservoirs with large river fish recruitment (Guy et al, ), current models treat reservoirs separately from the rivers they impound, which could explain the limited number of studies assessing upstream effects of reservoirs. Studies on fish distributions between or within reservoir and riverine habitats treat reservoirs as strictly lentic habitats and often consider these artificial systems as barriers themselves (Buckmeier, Smith, Fleming, & Bodine, ; Falke & Gido, ; Taylor, Knougt, & Hiland, ). In reality, there is not an abrupt change from riverine to reservoir environments but more gradual change as one moves through the riverine, transition, and lacustrine zones within a reservoir (Thornton, ).…”

Evidence for Serial Discontinuity in the Fish Community of a Heavily Impounded River

“…Moreover, reservoirs impounded on the low ends of rivers may include in their riverine upper reaches extensive floodplains periodically inundated by fluctuating reservoir water levels that to a degree mimic natural inundations. These upper reaches can support distinct and speciose fish assemblages that benefit from periodic connections between the reservoir, the floodplain environments and associated wetlands (Buckmeier et al, 2014;Miranda et al, 2014). Such connectivity may also benefit riverine species whose juveniles require access to floodplains.…”